I have the same issue. When I plug my adapter for my phone in the car that is exactly what happens. Have not had a chance to take it into the dealership yet. Does any one here have a response. I think it's probably the adapter. Might have to purchase the one Mercedes Benz give you when you purchase your call. That one got damaged so I've tried several but to no avail.
What’s crazy is that I take the car to the dealership I show the serviceman the issue... plug in... and it’s fixed!
I didn’t do anything different. Mercedes said to try to log out of everything Apple related... restart phone... then log back in ... then try.